1. Field of the Invention
This invention relates to the field of electrical generation. More particularly, it relates to the field of generating units of the type that convert the kinetic energy of ocean wave into electrical energy usable for consumption, conversion and/or transmission for a variety of purposes.
2. Description of the Prior Art
Electrical energy, the power to light the darkness, to run machines, to power television and telephone communication systems, to provide fresh water, and other processes, is needed by mankind in constantly increasing amounts. Virtually every mechanical, electrical and chemical machine or process requires the input of electrical energy. Conventional sources of electrical energy are presently subject to a variety of pressures. For instance, nuclear power is becoming less attractive because of safety reasons; the use of coal is being scaled back for environmental reasons; oil is becoming scarce for political reasons; and, supplies of natural gas are being used up at an alarming rate. Accordingly, another source of electrical energy is vitally needed to sustain the earth and its inhabitants in their continuing lifestyles.
The ocean, with its seemingly endless crashing of waves, historically has been considered a potential source of useful energy. In addition, ocean waves have caused an enormous amount of erosion to coastal regions. To capture all or a portion of this wave energy would not only supplement the rising need for electricity but would have far-reaching beneficial effects on the various coastal areas of the world.
For instance, it has been empirically calculated that capturing only one-half of the energy of the ocean wave that are 12 to 14 inches high and driven by a wind speed of 10 knots per hour, would yield power on the order of 200 watts per meter of wave front. Capturing one-half of higher waves, driven by a wind speed of 20 knots per hour, would yield power on the order of 10,000 watts or 10 kilowatts per meter of wave front. Capturing 90% of that power would increase the energy yields from 200 to 700 watts per meter and 10 to 42 kilowatts per meter, respectively. Should the wind increase in velocity to 50 knots per hour, a 90% capture of the energy would yield over 10 megawatts per meter. Empirical data shows that yearly average power densities available along coastal areas of the world vary from values of a few kilowatts per meter of wave front up to about 100 kilowatts per meter of wave front.
It can readily be seen therefore, that extraction of energy from the ocean can indeed be large and favorable to the inhabitants of this planet. In fact, under optimum circumstances, the continental United States could theoretically extract nearly 1 trillion kilowatt hours of energy annually, thus approaching present levels of hydroelectric energy production. In addition, high efficiency extraction of this energy from wave fronts approaching the shoreline would reduce the waves to near sea level in height and substantially reduce the erosive effects of pounding seas on our coast lines.
There have been numerous attempts to harness the power of ocean waves. Virtually all of them have failed to receive widespread acceptance. The various reasons for failure appear to range from the uneconomical nature of previous approaches to a failure to understand the basis of wave motion. The more simplified prior art attempts concern air turbines mounted over the wave fronts ducted to allow the wave fronts to force air up and down through the turbine blades to drive a turbine-electrical generator unit. Another form utilizes a sealed container mounted slightly below the surface of the sea where the top of the container is flexible. Intake and exhaust ports in the container are equipped with one-way valves and allow the container to pump liquids when the flexible top of the container rises and falls with the wave fronts.
Another invention, known as "Salter's Duck", includes an elongated member mounted at one end on a shaft and placed in the wave fronts. As the waves wash over the member (the ducks' "bill"), it rises and falls and rotates the shaft. Still another form utilizes an ordinary paddle wheel mounted on a shaft and set upright in the wave fronts to be turned by the wave fronts as they "go by". Yet another form of prior art includes a conveyor belt containing "impact" clips that extend outward therefrom, the belt is mounted parallel above the wave fronts so that the clips are struck by the advancing waves to move the belt and turn a pair of shafts.
Much of the non-acceptance of these inventions is based upon the difficulty of maintaining the devices in operable condition. Wave action constantly pounds the support structures as well as the conversion unit and, in many cases, literally breaks up the units so that they are no longer operable. In addition, elements that are to be driven by the advancing waves are often mounted on shafts that become corroded by the action of sea water and wind over a short period of time. Larger units require more massive structures and thereby impart a problem with friction and momentum such that the devices only become operable under extreme wave conditions and then are pounded by the heavy waves.
Non-acceptance has also stemmed from a failure to understand wave action. Water really doesn't move horizontally with the wave motion as much as it does in a circular motion during wave action. Many of the prior art devices are based upon the premise that water will migrate far more in the horizontal plane than in the vertical plane. In reality, the water particles move under an influence of both vertical forces and horizontal forces to trace a circle or elliptical path in a vertical plane during wave action.
In 1979, U.S. Pat. No. 4,151,423 was issued. This patent discloses a magnetohydrodynamic (MHD) electric generator for the direct energy conversion of the kinetic energy using ducted sea water flowing horizontally through a magnetic field, preferably through a constricted portion of the duct. This patent shows some embodiments wherein wave action is used to supplement the flow of water through the horizontally-arranged MHD duct; the supplemental water flow coming from a variety of pumps that are driven by wave energy. However, the MHD generator remains still in the water and requires either the slight horizontal movement of wave action to drive the water through the horizontally-arranged duct or, use that flow plus the supplemented flows stemming from the wave-generator devices, to produce electric energy by magnetohydrodynamic forces. Such a device clearly requires a substantial capital investment. The duct and its associated hardware are mounted just under the surface of the ocean and face all the aforesaid problems of pounding waves and corrosive wind/water action.
Another problem associated with prior art devices is that they are designed for installation at or just below the surface of the ocean. Air bubbles and debris are prevalent at this level and often interfere with the planned path of movement of the water through the device. In addition, where the devices utilize heavy flows of sea water, a substantial amount of cavitation is often encountered which severely decreases the efficiency of energy conversion.